The course of combustion on a combustion grate varies along the length of the grate. In the vicinity of the feed, the combustible material is dried and ignited. In an adjoining area, the combustible material burns intensively, the intensity decreasing toward the end of the grate until only burnt out and cooled cinder remains shortly before the end of the grate, which cinder falls into a correspondingly constructed discharge. Because of these different phases which the combustible material passes through on the way along the grate, it is necessary to regulate the primary air supply various ways. This was previously effected by providing underblast zones below the grate which are divided in the longitudinal direction of the same, so that differing air quantities being are supplied to the latter in order to take into account the different burning phases. The primary air supply is regulated to form the individual underblast zones according to distribution curves which are calculated beforehand and can be adapted to the respective prevailing conditions by also observing the furnace bed. It is also known to regulate the furnace output as a function of the O.sub.2 moist content measured in the combustion gases and/or the furnace temperature and/or the steam mass flow. In this case as well, it is governed by a computationally and empirically determined distribution of the primary air quantity with reference to the individual underblast zones.
A disadvantage in this type of furnace output regulation is the fact that the adjustment and distribution of the primary air is effected with reference to the grate width according to a mean value of the combustible material quality and that different qualities of combustible material and quantities of combustible materials are not taken into account with reference to the width. This results in a burning behavior which varies from place to place and in alternating air surplus indexes which counteract the attempt to achieve a uniform temperature profile in the furnace of the incineration plant. This can have disadvantageous consequences not only for the thermal behavior (efficiency factor) but also with respect to the emission of harmful gases.
The object of the invention is to improve the furnace output regulation in such a way that an optimal burning behavior and accordingly lower emission values, i.e. a lower environmental loading, and a thermal efficiency factor which is as uniform as possible, (a uniform steam production), is achieved along the entire combustion grate surface independently of the respective quality of combustible material.
This object is met, according to the invention, in that the primary air supply is also regulated differently by zones in the transverse direction of the combustion grate and in that the individual combustion zones are monitored and the primary air quantities are supplied to the individual combustion zones corresponding to the burning behavior of the combustible material prevailing in the respective combustion zones.
Different qualities of combustible material and different distributions of combustible material can be taken into account by means of this method, according to the invention, in such a way that an optimum combustion state prevails at all places on the combustion grate. This results in lower emission values and a high thermal efficiency factor of the plant.
The monitoring of the individual combustion zones can be effected by means of temperature measurement at a corresponding number of locations above the combustion zones in the furnace.
According to a preferred construction of the method, according to the invention, the monitoring of the individual combustion zones can be effected by means of video or thermographic cameras.
The apparatus for implementing the method with a combustion grate in which the primary air supply is effected along underblast zones divided in the longitudinal direction of the combustion grate is characterized in that the underblast zones are also divided in the transverse direction of the combustion grate and in that a monitoring device is provided for determining the burning behavior of the combustible material along the individual combustion zones assigned to the respective underblast zones.
The monitoring device can comprise the thermal elements assigned to the individual combustion zones, so that it is possible to record a temperature profile in the furnace and to influence the primary air supply in the individual combustion zones in a corresponding manner. In so doing, it is advantageous if the thermal elements are arranged between 5 and 15 m above the combustion zones.
In another construction of the invention, the monitoring device preferably comprises a thermographic or video camera, a monitor and a freely programmable computer which resolves the recorded image into individual picture lines and picture points and compares the digital values obtained in this way, which represent a measurement for the combustion bed temperature, the flame radiation or the brightness on the respective combustion zone, with preselected standard values and triggers a corresponding regulating process when there is a deviation. This type of monitoring is particularly advantageous, since the monitoring can be directed to every individual point of the combustion grate, so that an extremely sensitive regulation is possible.
The invention is explained in the following with the aid of embodiment examples of devices for implementing the method according to the invention, which devices are shown in the drawing.